Core Connections Algebra 2, 2013
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Core Connections Algebra 2, 2013 View details
1. Section 4.1
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Exercise 27 Page 176

Practice makes perfect
a Let's first isolate the square root in the given equation.
sqrt(2x-1)-x=-8
sqrt(2x-1)=x-8
Now we can raise each side of the equation to the power of 2.
sqrt(2x-1)=x-8
(sqrt(2x-1))^2=(x-8)^2
â–Ľ
Simplify
2x-1=(x-8)^2
2x-1=x^2-16x+64
0=x^2-18x+65
x^2-18x+65=0
We will use the Quadratic Formula to solve the given quadratic equation. ax^2+ bx+ c=0 ⇔ x=- b± sqrt(b^2-4 a c)/2 a We first need to identify the values of a, b, and c. x^2-18x+65=0 ⇔ 1x^2+( -18)x+ 65=0 We see that a= 1, b= -18, and c= 65. Let's substitute these values into the Quadratic Formula.
x=- b±sqrt(b^2-4ac)/2a
x=- ( -18)±sqrt(( -18)^2-4( 1)( 65))/2( 1)
â–Ľ
Solve for x and Simplify
x=18±sqrt((-18)^2-4(1)(65))/2(1)
x=18±sqrt(324-4(1)(65))/2(1)
x=18±sqrt(324-4(65))/2
x=18±sqrt(324-260)/2
x=18±sqrt(64)/2
x=18± 8/2
The solutions for this equation are x= 18± 82. Let's separate them into the positive and negative cases.
x=18± 8/2
x_1=18+8/2 x_2=18-8/2
x_1=26/2 x_2=10/2
x_1=13 x_2=5
Using the Quadratic Formula, we found that the solutions of the given equation are x_1=13 and x_2=5. Finally, we will check our solutions by substituting their values into the original equation. Let's start with x=13
sqrt(2x-1)-x=-8
sqrt(2( 13)-1)- 13? =-8
â–Ľ
Simplify left-hand side
sqrt(26-1)-13? =-8
sqrt(25)-13? =-8
5-13? =-8
-8=-8
We see that x=13 satisfies the original equation. Now we will check x=5 in the same way.
sqrt(2x-1)-x=-8
sqrt(2( 5)-1)- 5? =-8
â–Ľ
Simplify left-hand side
sqrt(10-1)-5? =-8
sqrt(9)-5? =-8
3-5? =-8
-2≠-8
However, we found that x=5 is extraneous because it does not satisfy the original equation.
b Let's first isolate the square root in the given equation.
sqrt(2x-1)-x=0
sqrt(2x-1)=x
Now we can raise each side of the equation to the power of 2.
sqrt(2x-1)=x
(sqrt(2x-1))^2=x^2
2x-1=x^2
0=x^2-2x+1
x^2-2x+1=0
We will use the Quadratic Formula to solve the given quadratic equation. ax^2+ bx+ c=0 ⇔ x=- b± sqrt(b^2-4 a c)/2 a We first need to identify the values of a, b, and c. x^2-2x+1=0 ⇔ 1x^2+( -2)x+ 1=0 We see that a= 1, b= -2, and c= 1. Let's substitute these values into the Quadratic Formula.
x=- b±sqrt(b^2-4ac)/2a
x=- ( -2)±sqrt(( -2)^2-4( 1)( 1))/2( 1)
â–Ľ
Solve for x and Simplify
x=2±sqrt((-2)^2-4(1)(1))/2(1)
x=2±sqrt(4-4(1)(1))/2(1)
x=2±sqrt(4-4)/2
x=2±sqrt(0)/2
x=2/2
x=1
Using the Quadratic Formula, we found that the solution of the given equation is x_1=1. Finally, we will check our solution by substituting its value into the original equation.
sqrt(2x-1)-x=0
sqrt(2( 1)-1)- 1? =0
â–Ľ
Simplify left-hand side
sqrt(2-1)-1? =0
sqrt(1)-1? =0
1-1? =0
0=0
We see that x=1 satisfies the original equation.